With reference to FIG. 1, a description will be given of operations of a mobile station UE for starting packet communications in response to an incoming call for the mobile station UE in a conventional packet communication system.
In Step S2001, a packet exchange SGSN sends paging for notifying the mobile station UE of the presence of an incoming call for the mobile station UE.
When noticing that the paging for the mobile station UE has been sent by the packet exchange SGSN in Step S2002, an AS (Access Stratum) function of the mobile station UE establishes a RRC (Radio Resource Control) connection with a radio network controller RNC in Step S2003.
In Step S2004, a NAS (Non Access Stratum) function of the mobile station UE establishes a signaling connection (C-plane path: control path) with the packet exchange SGSN.
In Step S2005, the packet exchange SGSN sends an “SMS (Short Message Service) Push” to the mobile station UE via the C-plane path. The “SMS Push” is a message for instructing the mobile station UE to establish a U-plane path with the packet exchange SGSN.
In Step S2006, in response to an incoming of the “SMS Push” sent by the packet exchange SGSN, an APL (Application Stratum) function of the mobile station UE sends a “start instruction” to the NAS function of the mobile station UE. The “start instruction” instructs the NAS function of the mobile station UE to establish a U-plane path with the packet exchange SGSN. Then, in Step S2007, the NAS function of the mobile station UE sends the “start instruction” to the AS function of the mobile station UE.
In Step S2008, in response to the “start instruction” received from the NAS function of the mobile station UE, the AS function of the mobile station UE calls to the packet exchange SGSN to thereby establish an RRC connection with the radio network controller RNC.
In Step S2009, when the C-plane path established in Step S2004 is now released, the NAS function of the mobile station UE establishes a C-plane path with the packet exchange SGSN.
In Step S2010, the NAS function of the mobile station UE establishes a U-plane path (data path) with the packet exchange SGSN.
Next, with reference to FIGS. 2 to 5, a description will be given of operations of a mobile station UE#1 for performing packet communications in response to an incoming call for the mobile station UE#1 when congestion occurs in the packet exchange SGSN in the conventional packet communication system.
Firstly, with reference to FIGS. 2 and 3, a first operation will be described.
As shown in FIGS. 2 and 3, in Step S3001, when detecting congestion in the packet exchange SGSN, the radio network controller RNC informs the mobile station UE#1 of restriction information for accepting an incoming call and restricting an outgoing call, namely, for restricting only PS calling (for example, VoIP (Voice over IP) communications and PoC (Push-to-Talk over Cellular) communications).
In the example of FIG. 2, the restriction information is set to restrict an outgoing call only from mobile stations each with a UE class (access class indicating a type of a mobile station) of any of “5” to “9”.
Thus, a mobile station UE#3 with the UE class of “0” can accept both an outgoing call and an incoming call even when receiving the restriction information, since the restriction information does not restrict the outgoing call and the incoming call of the mobile station UE#3 with the UE class of “0”.
Here, an AS (Access Stratum) function of the mobile station UE#1 receives and stores the restriction information.
In Step S3002, the packet exchange SGSN sends paging for notifying the mobile station UE#1 of the presence of an incoming call for the mobile station UE#1.
When noticing, in Step S3003, that the paging sent by the packet exchange SGSN is for the mobile station UE#1 and that the incoming of the paging is accepted in the mobile station UE#1 on the basis of the restriction information, the AS function of the mobile station UE#1 establishes an RRC connection with the radio network controller RNC in Step S3004.
In Step S3005, a NAS function of the mobile station UE#1 establishes a C-plane path with the packet exchange SGSN.
In Step S3006, the packet exchange SGSN sends an “SMS Push” to the mobile station UE#1 via the C-plane path. The “SMS Push” is a message for instructing the mobile station UE#1 to establish a U-plane path with the packet exchange SGSN.
In Step S3007, in response to the incoming of the “SMS Push” sent by the packet exchange SGSN, an APL function of the mobile station UE#1 sends a “start instruction” to the NAS function of the mobile station UE#1. The “start instruction” instructs the NAS function of the mobile station UE#1 to establish a U-plane path with the packet exchange SGSN. Then, in Step S3008, the NAS function of the mobile station UE#1 sends the “start instruction” to the AS function of the mobile station UE#1.
When noticing in Step S3009 that the PS calling is restricted in the mobile station UE#1 with the UE class of “5”, on the basis of the restriction information, the AS function of the mobile station UE#1 cannot call to the packet exchange SGSN in Step S3010 even if receiving the “start instruction” from the NAS function of the mobile station UE#1. This makes it impossible to establish a U-plane path with the packet exchange SGSN.
Secondly, with reference to FIG. 4, a second operation will be described. In an example of the mobile communication system in FIG. 4, assume that an “SMS Push” is sent from a CS domain while a response to the “SMS Push” is sent to a PS domain.
As shown in FIG. 4, in Step S3101, when detecting congestion in the packet exchange SGSN, the radio network controller RNC informs the mobile station UE#1 of restriction information for accepting an incoming call and restricting an outgoing call, namely, for restricting only PS calling.
Here, the AS (Access Stratum) function of the mobile station UE#1 receives and stores the restriction information.
In Step S3102, a circuit exchange MSC/VLR sends paging for notifying the mobile station UE#1 of the presence of an incoming call for the mobile station UE#1.
When noticing, in Step S3103, that the paging sent by the circuit exchange MSC/VLR is for the mobile station UE#1 and that the incoming of the paging is accepted in the mobile station UE#1, on the basis of the restriction information, the AS function of the mobile station UE#1 establishes an RRC connection with the radio network controller RNC in Step S3104.
In Step S3105, the NAS function of the mobile station UE#1 establishes a C-plane path with the circuit exchange MSC/VLR.
In Step S3106, the circuit exchange MSC/VLR sends an “SMS Push” to the mobile station UE#1 via the C-plane path. The “SMS Push” is a message for instructing the mobile station UE#1 to establish a U-plane path with the circuit exchange MSC/VLR.
In Step S3107, in response to the incoming of the “SMS Push” sent by the circuit exchange MSC/VLR, the APL function of the mobile station UE#1 sends a “start instruction” to the NAS function of the mobile station UE#1. The “start instruction” instructs the NAS function of the mobile station UE#1 to establish a U-plane path with the packet exchange SGSN.
Here, in Step S3108, the NAS function of the mobile station UE#1 generally establishes a C-plane path with the packet exchange SGSN instead of sending the “start instruction” to the AS function of the mobile station UE#1, when judging that the mobile station UE#1 has established the RRC connection with the radio network controller RNC.
However, when noticing, in Step S3108, that the PS transmission is restricted in the mobile station UE#1, the NAS function of the mobile station UE#1 cannot establish a C-plane path with the packet exchange SGSN, and cannot establish a U-plane path with the packet exchange SGSN either.
Thirdly, with reference to FIG. 5, a third operation will be described. Note that, operations of Steps S3201 to S3206 in FIG. 5 are the same as those of Steps S3001 to S3006 in FIG. 3, and therefore descriptions thereof will be omitted.
In Step S3207, in response to the incoming of the “SMS Push” sent by the packet exchange SGSN, the APL function of the mobile station UE#1 sends a “start instruction” to the NAS function of the mobile station UE#1. The “start instruction” instructs the NAS function of the mobile station UE#1 to establish a U-plane path with the packet exchange SGSN.
Here, in Step S3208, the NAS function of the mobile station UE#1 generally establishes a U-plane path with the packet exchange SGSN instead of sending the “start instruction” to the AS function of the mobile station UE#1, when judging that the mobile station UE#1 has established the C-plane path with the packet exchange SGSN.
However, when noticing, in Step S3208, that the PS transmission is restricted in the mobile station UE#1, the NAS function of the mobile station UE#1 cannot establish a U-plane path with the packet exchange SGSN.
Non-patent Document 1: 3GPP TS23.040, “Technical realization of the Short Message Service (SMS)”